Platinum-iron alloy, especially for jewelry

ABSTRACT

Platinum—iron alloys that contain 95-96 wt % Pt, 2-3 wt % Fe, and 20-3 wt % Ru and/or Ir, and are suitable especially for the fabrication of jewelry.

BACKGROUND OF THE INVENTION

[0001] The invention concerns platinum—iron alloys with an iron content of 2-4 wt. %, which are suitable especially for the fabrication of jewelry.

[0002] Pure platinum, like fine gold, is relatively soft and, also like gold, is used primarily to produce alloys for articles of jewelry. The platinum content of these kinds of alloys is usually 950/1,000. Typical alloying components are Ru, Cu, and occasionally Rh and Ir. These elements are relatively expensive (Ru, Ir, Rh) or have little effect on the strength of the alloy (Cu and Ir). Nickel is no longer used for this purpose due to the risk of allergic reactions.

[0003] Therefore, in the jewelry sector, there is a demand for alloys that are sufficiently strong, easy to work, resistant to corrosion and physiologically unobjectionable, and that do not add significant additional cost beyond the price of platinum.

[0004] It is well known that platinum and palladium alloys can be hardened with elements such as Fe, Co, B, or Si by a special alloying method, in which intermetallic phases are formed (U.S. Pat. No. 5,518,556, col. 1, lines 24-30). Hardness values of 300 kp/mm² are achieved.

[0005] Platinum—iron—copper alloys that contain 84-96% Pt, 1-10% Fe, and 1-10% Cu have also been developed (JP Kokai No. 61 [1986]-281,843). Cu is added because it forms an intermetallic compound with Pt. A similar system with Pt—Ga—Fe has been proposed (JP Kokai No. 61[1986]-272,333). Furthermore, Pt—Co alloys have been described, which may also contain 0.5-5% of the elements W, Mo, Ti, V, and/or iron (JP Kokai No. 61[1986]-034,139). Pt—Pd alloys with an Re component and up to 3% Ni, Fe, or Co are also known (JP Kokai No.2[1990]-043,332).

[0006] In addition, inexpensive white gold and yellow gold alloys with a low gold content are known, which may contain up to 3% iron. A higher iron content causes tarnishing of the material (U.S. Pat. Nos. 4,396,578 and 4,446,102).

[0007] JP 61[1986]-076,633 A1 describes alloys from which gemmy accessories, i.e., products that resemble gems, are fabricated, which have an especially durable luster after facets have been ground. The alloys are produced by alloying 0.1-5 wt. % Ru and 2-15% Fe, Ni, and/or Co with Pt—Pd alloys.

[0008] JP 3[1991]-100,159 describes darkened Pt alloys: 3-20% of one or more of the metals Cu, Fe, Co, and Ti are alloyed with platinum. The surface is darkened by heat treatment in an oxidizing atmosphere and then cooling.

SUMMARY AND DESCRIPTION OF THE INVENTION

[0009] According to the present invention, alloys containing 95-96% Pt, 2-3% Fe, and 2-3% Ru and/or Ir are extremely well suited for the fabrication of jewelry due to their hardness, workability and resistance to corrosion.

[0010] The alloys are usually cast from melts under a shielding gas and then shaped. After shaping, they may be subjected to a heat treatment, possibly under a shielding gas, to improve their mechanical properties.

[0011] A relatively large portion of jewelry platinum is used in wedding bands, which are produced by sawing blanks from tubes and then further working the blanks by suitable measures, such as milling, drawing, forging, and polishing.

[0012] Of course, the alloys are suitable for articles of jewelry in the broader sense, including jewelry worn on the body or on clothing, such as rings, bangles, and stickpins, as well as such articles as wristwatches, pocket watches, toothpicks, and status-symbol items, such as ballpoint pens, letter openers, pocketknife handles, and the like.

[0013] The following example explains the invention in greater detail. The percentages in the example as well as those mentioned previously are percentages by weight.

SPECIFIC EXAMPLE I. Production and Shaping of a PtFe3.0Ru1.8 Alloy

[0014] 5 kg of PtFe3.0Ru1.8 were melted inductively in an Ar atmosphere, cast in a Cu ingot mold to form a bar with a cross section of 45×45 mm, forged into a cylindrical bar of diameter (Ø) 36 mm, and turned to form a hollow cylinder (outside Ø32 mm, inside Ø22 mm, length 100 mm). A tube (outside Ø20 mm, wall thickness 1.5 mm) was produced from the alloy by conventional tube drawing. The material could be readily worked in every way.

[0015] The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims. 

We claim:
 1. An alloy comprising: 95-96 wt % Pt; 2-3 wt % Fe, and 2-3 wt % of at least one of Ru and Ir.
 2. An alloy as defined in claim 1, wherein the alloy has of 95.2 wt % Pt, 3 wt % Fe, and 1.8 wt % Ru.
 3. An article of jewelry comprising an alloy of 95-96 wt % Pt; 2-3 wt % Fe, and 2-3 wt % of at least one of Ru and Ir. 